ACANTHOTHECA. 51 



to the thickness of a goose-quill ; it is much broader 

 anteriorly than posteriorly ; the two pairs of hooks, 

 which are situated near the mouth, can be re- 

 tracted into as many distinct cavities (whence this 

 genus derives its name). The female is oviparous. 



The Pentastoma live in the frontal sinuses, in 

 the larynx, trachea, and lungs, or are contained in 

 cysts upon the surface of organs. 



These parasites have been observed in man, and 

 in the mammiferae, especially in. reptiles. They 

 seem to be more common in Brazil than m. other 

 parts of the world. 



The two species which have been found in man 

 are in the larval condition. 



Pentastomum Constrictum. 



This species has received its name from the 

 transverse constrictions of its body, which, conse- 

 quently presents an annulated appearance. The body 

 is also rounded off anteriorly, and terminates poste- 

 riorly in a truncated cone ; its integument possesses 

 no spiaes. 



This entozoon is about half an inch in length, 

 and one-twelfth of an inch in breadth. 



Pentastomum Denticulatum. 



The body of this worm is of a white colour, and 

 is larger in. front than behind ; it is convex upon its 

 upper, and flattened upon its lower surface ; it is 

 also annulated, and is covered with a number of 

 spines. 



This entozoon is probably the larva of the Pentas- 



E 2 



